Electroless metal coatings on machine components for enhanced performance are known in the art. The electroless coating process is typically used for enriching the surface of metallic components for protection against corrosion, wear, etc. For example, U.S. Published Application No. 2011/206532 relates to an electroless coating process including coating a substrate with an electroless coating and then heating to a specific temperature.
Some engines are assembled with surface hardened components. A nitriding process is widely used for surface hardening of the components. The nitriding process is a heat treatment process that diffuses nitrogen into the surface of the metallic component to create a case hardened surface. The component may be made from steel, iron, titanium, and the like. The component that is subjected to the nitriding process may already be in a hardened and tempered condition. This may allow for the nitriding process to take place at a temperature lower than the last tempering temperature. Further surface treatment, such as, for example, coating or cladding, may be conducted at a lower temperature than that of the nitriding temperature, in order to avoid damaging of the nitride hardened layer.
During operation, the nitrided surface of the component may be subjected to wear, cavitation, erosion, tear, corrosion, or other damage. The damage may be due to the application of higher force, surface strain, torsion, bending moment, or other environmental conditions. Damage to the nitrided surface may result in unsatisfactory performance, sometimes requiring replacement of the parts with new components. This may lead to an overall increase in costs.
Various methods for repairing these damaged components are known in the art. For example, micro arc welding and laser beam cladding can be used for coating a material on the nitrided surface. However, these techniques are thermal based repair processes that may damage a base material strength of the nitrided surface. High temperatures involved in thermal based repair processes can lead to out-gassing of nitrogen from the nitrided surface, causing a reduction in the hardness of the nitrided surface. The out-gassing of nitrogen may also lead to porosity issues in the coated material.
Other known techniques include chrome plating and High Velocity Fuel Oxygen (HVOF). However, the chrome plating technique is not environment friendly. In the HVOF method, bonding between the coated material and the nitrided surface is not metallurgical, thus affecting the bond strength.
Hence, there is a need of providing an improved method of repair for nitrided components.